Overplated thermally conductive part with EMI sheilding

ABSTRACT

A net-shape molded heat transfer component is provided which includes a thermally conductive core and a metallic coating for reflection of electromagnetic interference and radio frequency waves. The heat transfer component is formed by net-shape molding a core body from a thermally conductive composition, such as a polymer composition, and applying a metallic coating. The molded heat transfer part is freely convecting through the part, which makes it more efficient and has an optimal thermal configuration. Additionally, the part is shielded from electromagnetic interference and radio frequency waves, thus preventing the transfer of same into the circuitry housed by the part. In addition, the coating also seals the conductive polymer core against moisture infiltration, making the part well suited for telecommunications applications in potentially harsh environments.

BACKGROUND OF THE INVENTION

[0001] The present invention relates generally to the dissipation ofheat from heat generating surfaces and objects. More specifically, thepresent invention relates to apparatuses for dissipating heat generatedby such objects. In addition, the present invention relates to passivelyconducting heat away from heat generating objects by use of thermallyconductive composite materials while further shielding the device fromelectromagnetic interference (EMI).

[0002] In industry, there are various parts and components that generateheat during operation. For example, in the electronics andcommunications industries, it is well known that integrated circuitcomponents generate heat during operation. Various types of electronicdevice packages containing integrated circuit chips, such as satellitedishes, are such devices that generate heat. Often these devices containintegrated circuit systems with a tightly packed configuration thatrequires all of the components to be installed in close proximity to oneanother. These integrated circuit devices, particularly the mainprocessor chips, generate a great deal of heat during operation whichmust be removed to prevent adverse effects on operation of the systeminto which the device is installed. For example, the operational sectionof a satellite dish, containing many integrated circuit components, ishighly susceptible to overheating which could destroy the device itselfor cause the components within the device to malfunction.

[0003] There are a number of prior art methods to cool heat generatingcomponents and objects to avoid device failure and overheating, asdiscussed above. Since the space available within these devices isgenerally quite limited the heat must be conducted away from theheat-generating component for dissipation at the periphery of thedevice. In these cases, a heat-conducting device is commonly placed intocommunication with the heat generating surface at one end and a heatsink at the other to dissipate the heat therefrom. Such aheat-conducting device is typically constructed from a metal casing thatis charged with a conductive gas and serves primarily as a conductorwith little heat-dissipating characteristic, therefore requiring theinclusion of a heat sink device in the cooling system. A heat sinktypically includes a base member with a number of individual coolingmembers, such as fins, posts or pins, to assist in the dissipation ofheat and may be incorporated into the case of the heat generatingdevice. The geometry of the cooling members is designed to improve theamount of surface area of the heat sink that contacts the ambient airfor optimal heat dissipation. The use of such fins, posts or othersurface area increasing methods, in an optimal geometrical configurationgreatly enhances heat dissipation compared to devices with no suchadditional cooling members, such as a flat heat spreader.

[0004] To further enhance airflow and resultant heat dissipation, fansand devices have been used, either internally or externally. However,these external devices consume power and have numerous moving parts. Asa result, heat sink assemblies with active devices are subject tofailure and are much less reliable than a device that is solely passivein nature.

[0005] It has been discovered that more efficient cooling of electronicscan be obtained through the use of passive devices that require noexternal power source and contain no moving parts. It is very common inthe electronics industry to have many electronic devices grouped on asingle circuit board, such as a motherboard, modem, or “processor card”such as the Celeron board manufactured by Intel Corporation. Forexample, video cards, which are capable of processing millions ofpolygons per second, are also susceptible to overheating and needefficient and effective cooling, as do the CPUs discussed above. Videocards typically have at least one chip thereon that runs extremely hotto necessitate a cooling system designed to operate within smallclearances.

[0006] In the heat transfer industries, it has been well known to employmetallic materials for thermal conductivity applications, such as heatdissipation for cooling integrated circuit device packages. For theseapplications, such as device casings operating as heat sinks, themetallic material typically is tooled or machined from bulk metals intothe desired configuration. However, such metallic conductive articlesare typically very heavy, costly to machine and are susceptible tocorrosion. Further, the use of metallic materials commonly createselectromagnetic interference (EMI), which often detracts from theperformance of the device on which the heat sink is affixed. Finally,the geometries of machined metallic heat dissipating articles are verylimited to the inherent limitations associated with the machining ortooling process. As a result, the requirement of use of metallicmaterials which are machined into the desired form, place severelimitations on heat sink and heat conductor design particular when it isknown that certain geometries, simply by virtue of their design, wouldrealize better efficiency but are not attainable due to the limitationsin machining metallic articles. To compensate for these limitations,active cooling, such as by powered fans, must be employed to achieve therequisite cooling to prevent device failure.

[0007] It is widely known in the prior art that improving the overallgeometry of a heat-dissipating article can greatly enhance the overallperformance of the article even if the material employed is the same.Therefore, the need for improved heat sink geometries necessitated analternative to the machining of bulk metallic materials. To meet thisneed, attempts have been made in the prior art to provide moldedcompositions that include conductive filler material therein to providethe necessary thermal conductivity. The ability to mold a conductivecomposite enabled the design of more complex part geometries to realizeimproved performance of the part.

[0008] However, a drawback in the thermally conductive molded polymercompositions, loaded with metallic reinforcing materials such as copperflakes, is that they inherently absorb EMI and radio frequency waves. Asa result of their absorptive characteristics these materials effectivelyoperate as antennas absorbing EMI that could potentially interfere withthe operation of the device into which they have been incorporated. As aresult, the use of these conductive polymers in devices such assatellite components and receiver equipment is undesirable.

[0009] In view of the foregoing, there is a demand for a heatdissipation assembly that is thermally conductive and capable ofdissipating heat. There is a demand for a passive heat dissipationassembly with no moving parts that can provide heat dissipation withoutthe use of active components. In addition, there is a demand for acomplete heat sink assembly that can provide greatly enhanced heatdissipation over prior art passive devices with improved heat sinkgeometry. There is a demand for a heat sink assembly that can providethermal conductivity and dissipation in a compact configuration. Thereis a further demand for a net-shape molded heat dissipation assemblythat does not absorb EMI and is well suited for use in harshenvironments.

SUMMARY OF THE INVENTION

[0010] The present invention employs the advantages of prior art heattransfer and dissipation devices. In addition, it provides newadvantages not found in currently available devices and overcomes manydisadvantages of such currently available devices.

[0011] The invention is generally directed to a novel and unique, moldedthermally conductive component part that is net-shape moldable from athermally conductive polymer composition. The part of the presentinvention also includes a coating of EMI reflective material. Thepresent invention relates to a molded heat dissipating part thatconducts heat from a heat-generating source, such as an integratedcircuit component or electronic components on a computer circuit board,such as the operational section of a satellite dish.

[0012] The molded heat dissipation part of the present invention hasmany advantages over prior art in that it is injection molded from thethermally conductive polymer materials that enables the part to be madein complex geometries. These complex geometries enable the heatconductive and dissipative components of the part to be optimized to bemore efficient thus transferring and dissipating more heat. As a result,the molded part is freely convecting throughout, making the part moreefficient. The ability to injection mold the heat dissipation partpermits the optimal configuration to be realized and achieved. Since thepart is net-shape molded, valuable and costly fabrication time will besaved. Parts can be fabricated that, although complex in shape, requireno additional tooling, shaping or machining steps to reach the finalconfiguration. Parts can be designed in virtually any shape to beinstalled within tight clearances allowing the most efficient layout ofheat generating components while still allowing heat to be conducted tothe periphery of the device for effective dissipation. The presentmolded heat dissipation part can be designed to what is thermallyefficient while allowing the device to be designed in the most efficientmanner without the limitations imposed by the manufacturing andmechanical limitations of the prior art processes, such as brazing.

[0013] Another important feature of the new heat dissipating part is itsability to reflect EMI and RF waves. This is particularly important in asatellite dish environment, which is very EMI sensitive. Since themoldable conductive polymer inherently absorbs EMI and RF waves, thereis a danger that this interference will be conducted back into thecircuitry from which the heat is being dissipated. This interference isoften problematic and prevents the device from functioning properly. Toprevent the parts from absorbing EMI and RF, the part of the presentinvention is covered with a metallic coating to effectively reflect theEMI and RF waves and avoid the unwanted interference often encounteredin telecommunications applications. A coating of nickel-copper is apreferred coating and would serve the additional function of sealing theconductive polymer against water infiltration. This would protect thedevice for use in potentially harsh environments similar to those inwhich a great deal of telecommunications equipment is currentlyinstalled.

[0014] It is therefore an object of the present invention to provide aheat-dissipating device that can provide enhanced heat dissipation for aheat generating component or object.

[0015] It is an object of the present invention to provide aheat-dissipating device that can provide heat dissipation for integratedcircuit devices, such as a satellite dish or telecommunicationsequipment.

[0016] It is a further object of the present invention to provide aheat-dissipating device that has no moving parts.

[0017] Another object of the present invention is to provide aheat-dissipating device that is completely passive and does not consumepower.

[0018] A further object of the present invention is to provide a heatdissipation device that is inexpensive to manufacture.

[0019] Another object of the present invention is to provide a heatdissipation device that has a thermal conductivity greater thatconventional heat sink designs.

[0020] An object of the present invention is to provide a heat transferpart that is net-shape moldable and can be configured into complexgeometries to allow optimal integrated circuit configuration.

[0021] Yet another object of the present invention is to provide amolded heat transfer part that is shielded from absorption ofelectromagnetic interference and radio frequency waves.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The novel features which are characteristic of the presentinvention are set forth in the appended claims. However, the invention'spreferred embodiments, will be best understood by reference to thefollowing detailed description taken in connection with the accompanyingdrawings in which:

[0023]FIG. 1 is a perspective view of the heat component part of thepresent invention;

[0024]FIG. 2 is a cross-sectional view through the line 2-2 of FIG. 1;and

[0025]FIG. 3 is a side elevational view of the thermally conductive partof FIG. 1 in thermal communication with a heat-generating device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0026] Referring to FIG. 1, a perspective view of a sample net-shapemolded heat transfer part 10 with an EMI coating 13 of the presentinvention is shown. The net-shape molded part 10 includes air flowgrooves 11 and mounting holes 12 therethrough, which can be moldeddirectly into the part rather than machining them in a subsequent stepas in the prior art. Alternately, these mounting holes 12 may bedrilled.

[0027] In FIG. 2, a cross-sectional view of the molded heat transferpart 10 of the present invention is shown while FIG. 3 illustrates aside elevational view of the part mounted 10 on a device 16 to becooled. As best seen in FIG. 2, the molded heat transfer part 10includes a heat conductive polymer core 13. An EMI and RF reflectivecoating 14 is applied, preferably on the entire outer surface 18 of thepart. The molded heat transfer part 10 is net-shape molded, such as byinjection molding, into a unitary structure from thermally conductivematerial, such as a thermally conductive polymer composition. Thethermally conductive polymer composition includes a base polymer of, forexample, a liquid crystal polymer that is loaded with a conductivefiller material, such as copper flakes or carbon fiber (not shown).Carbon fiber is preferred because it cannot transfer electricity yet isstill highly thermally conductive. Details of the polymer compositionitself are not shown as they are well known in the art. The EMI and RFreflective coating 14 is preferably nickel-copper. Other base materialsand reflective coatings may be used and still be within the scope of thepresent invention. Also, the heat transfer part 10 of the presentinvention is net-shape molded which means that after molding it is readyfor use and does not require additional machining or tooling to achievethe desired configuration of the part 10.

[0028] As described above, the ability to injection mold a thermallyconductive part 10 rather than machine it has many advantages. As can beseen in FIGS. 1 and 2, grooves 11 increase the surface area of the part10 available for heat transfer, and mounting holes 12, can be moldedinto the part 10 in a one-step process to facilitate mounting to anobject to be cooled. This is followed by a simple plating process to addthe reflective coating 14 to the surface of the entire part 10. Thefigures illustrate one of many embodiments of the invention where athermally conductive composition is net-shape molded into a thermallyconductive heat transfer part 10. The configuration shown in the figuresis by way of example. Other configurations can be employed and still bewithin the scope of the present invention.

[0029] As shown in FIG. 3, the installation of the heat transfer part 10of the present invention onto a heat generating integrated circuitdevice 15 is shown, by way of example. The circuit board 15 includes asemiconductor device 16 mounted thereon that runs hot and is need ofheat dissipation to avoid failure. The bottom side 19 of the heattransfer part 10 is positioned in flush thermal communication with thetop surface 20 of semiconductor device 16. Fasteners 17, such asthreaded screws, engage with circuit board 15 to secure the heattransfer part 10, via apertures 12, in thermal transfer relationshipwith the top side 20 of semiconductor device 16. Other different typesof fasteners 17 and connection methods may be employed for this purpose,such as spring clips (not shown).

[0030] The reflective coating 14 on the part is employed to preventabsorption of EMI and RF waves by the heat transfer part 10 that couldthen be conducted back to the semiconductor 16 over the same pathway bywhich heat is dissipated. This embodiment of the present invention isparticularly well suited for use in telecommunications applicationswhere the heat transfer part 10 is subjected to constant bombardment byEMI and RF waves that could cause malfunction or failure of the verysemiconductor 16 it was installed to cool and protect.

[0031] It should be understood that the application shown in FIG. 3 ismerely an example of the many different applications of the presentinvention and is for illustration purposes only. The heat transfer part10 could be fabricated in many shapes for incorporation into or housingsfor telecommunication applications by a modified embodiment inaccordance with the present invention and may be modified to cool a widearray of heat generating objects.

[0032] In accordance with the present invention, a net-shape molded heattransfer part 10 is disclosed that is easy and inexpensive tomanufacture and provides thermal transfer that is superior to prior artmetal-machined heat transfer parts and device casings. In addition, thepart 10 includes shielding capability that further protects the device,to which it is connected, from the deleterious effects of EMI and RFwaves.

[0033] It would be appreciated by those skilled in the art that variouschanges and modifications can be made to the illustrated embodimentswithout departing from the spirit of the present invention. All suchmodifications and changes are intended to be covered by the appendedclaims.

What is claimed is:
 1. A net-shape molded heat transfer part,comprising: a core of thermally conductive material having an outersurface; and a metallic coating disposed on said outer surface of saidcore.
 2. The net-shape molded heat transfer part of claim 1, whereinsaid thermally conductive core is a polymer composite material.
 3. Thenet-shape molded heat transfer part of claim 2, wherein said polymercomposite includes a base matrix and a conductive filler loaded therein.4. The net-shape molded heat transfer part of claim 3, wherein saidconductive filler is copper flakes.
 5. The net-shape molded heattransfer part of claim 3, wherein said conductive filler is carbonfiber.
 6. The net-shape molded heat transfer part of claim 1, whereinsaid metallic coating is an electromagnetic interference reflectivecoating.
 7. The net-shape molded heat transfer part of claim 1, whereinsaid metallic coating is a radio frequency wave reflective coating. 8.The net-shape molded heat transfer part of claim 1, wherein saidmetallic coating is a copper-nickel coating.
 9. A method of forming athermally conductive part, comprising the steps of: molding a part of athermally conductive composite material into a net-shape moldedconfiguration; and applying a metallic coating over said part.
 10. Themethod of claim 9, further comprising the step of: providing anelectromagnetic interference reflective layer about said part.
 11. Anet-shape moldable heat transfer part, comprising: A core of thermallyconductive polymer composite including a base matrix of polymer materialloaded with thermally conductive filler; and A metallic coating on saidcore; said core being sealed from moisture and sealed fromelectromagnetic interference and radio frequency waves. a metalliccoating to substantially seal the polymer core against moistureinfiltration.